The present invention relates generally to label assemblies of the type comprising a plurality of labels releasably mounted on a common backing and relates more particularly to techniques for proper registration of individual labels of such assemblies in label printing and/or dispensing devices.
It is commonplace for articles of commerce to be labeled with one or more labels, many of which contain various items of information, such information including, but not being limited to, the trademark and/or generic name of the article, instructions for use and/or care of the article, article size information, article pricing information, a serial number uniquely identifying each article, authenticity information, and the like.
One type of label that is commonly used to label articles of commerce is an adhesive-backed label. Often, such a label is formed as part of a label assembly comprising a plurality of labels spaced apart from one another and releasably mounted on a common web of material. Referring now to FIGS. 1(a) and 1(b), there are shown top and side views, respectively, of a conventional label assembly 11 of the aforementioned type. As can be seen, label assembly 11 comprises a backing 13, a release coating 15 applied to the top surface of backing 13 (backing 13 and release coating 15 jointly defining a common web 16), and a plurality of labels 17 spaced apart on release coating 15. (Typically, labels 17 are spaced apart from one another by a distance of approximately ⅛ to ¼ inch.) Label assembly 11 is typically wound into a roll and then unwound as needed. (Alternatively, instead of being wound into a roll, label assembly 11 may be stored in a fanfold, which may be unfolded as needed.)
Backing 13 is typically a length of polyethylene terephthalate film, a length of Mylar® polyester film, or a strip of paper. Release coating 15 is typically a silicone or wax release. Each of labels 17 typically includes an adhesive layer 19 and a face sheet 21. Adhesive layer 19, which comprises a pressure-sensitive adhesive, is in direct contact with release coating 15. Face sheet 21, which is positioned directly over adhesive layer 19, is typically made of a print-receptive material, such as paper.
Although the particular information appearing on face sheet 21 may be printed by the label manufacturer, with the resultant pre-printed labels then being shipped to an industrial user of the label for application of the label to an article, it has become increasingly more common for some or all of such printed information to be printed by the industrial user of the label on an “as needed” or “on demand” basis.
In any event, whether the printing is done by the label manufacturer or by the industrial user, such printing is typically performed using an automated printing system in which the label assembly is progressively unwound from a roll (or unfolded from a fanfold) and individual labels are successively advanced to a printer head at a printing station, where the printer head prints the desired information onto each label, and the label assembly is then re-wound (or re-folded) after the printing station or dispensed. The latter is for manual or automatic application of the label to the article.
As can be appreciated, it is very important that the individual labels be registered properly with the printer head so that the information printed from the printer head is properly aligned with each label. Consequently, most printers include some type of registration sensor for sensing the leading edge of each label (also referred to as “the top of form”) in order to synchronize printing with the desired positioning of the label. One of the most common types of registration sensors present in label printing systems is an optical transmission sensor. Referring now to FIG. 2, such a sensor 31 typically comprises a light source 33 and a light detector 35, light source 33 and light detector 35 being positioned above and below, respectively, (or below and above, respectively) label assembly 11. As can be seen, light source 33 is positioned to illuminate label assembly 11, and light detector 35 is positioned to detect the light transmitted through assembly 11. Sensor 31 makes use of the fact that the amount of light passing through label assembly 11 is greater in the areas between labels 17 than in the areas in which labels 17 are present. (To make even more conspicuous the difference in light transmission between the areas between labels 17 and the areas in which labels 17 are present, one could provide holes in web 16 in the areas between labels 17.) Another registration sensor of the type present in label printing systems is an optical reflection sensor. As seen in FIG. 3, such a sensor 41 typically comprises a light source 43 positioned below a label assembly 51 for illuminating the bottom of label assembly 51 and a light detector 45 positioned below label assembly 51 for detecting the light reflected off the bottom of label assembly 51. In order for optical reflection sensor 41 to detect the leading edge of a label 17, a dark or opaque registration or eye mark 53 is printed on the bottom of backing 13 along the leading edge of each label 17. Bottom and side views of a portion of label assembly 51 are shown in FIGS. 4(a) and 4(b), respectively. As can be seen, eye mark 53 is printed on the bottom of backing 13 across the entire width of backing 13 at the leading edge of each label 17. Typically, eye mark 53 has a width w of about one-quarter to three-eighths of an inch, viewed along the longitudinal axis of label assembly 51. Alternative label assemblies 51-1 through 51-3 having differently positioned eye marks 53-1 through 53-3, respectively, are shown in FIGS. 5(a) and 5(b), FIGS. 6(a) and 6(b), and FIGS. 7(a) and 7(b), respectively, eye marks 53-2 and 53-3 being aligned with the “matrix strip” between adjacent labels 17, as opposed to being aligned with labels 17, themselves. One advantage of eye marks that extend across the entire width of the web, as is the case with marks 53 and 53-2, is compatibility with a wide range of printers having different sensor cross-web locations.
Still another, but even less common, registration sensor is a capacitive sensor, which makes use of differences in the dielectric characteristics of the label assembly in the areas between labels and the areas within labels in order to identify the leading edge of each label.
Registration sensors of the type described above not only are used to synchronize printing with the arrival of a label at a printer head but also are used by many printers to determine when the printer is out of labels. (In some cases, a separate but similar sensor is used for sensing when the printer is out of labels.) More specifically, if the registration sensor does not sense the leading edge of a label within a certain interval defined as the next label position or, in some cases, within the next two or three label positions from a previously sensed label, many printers are designed to determine that the last label of the label assembly has been fed, causing the printer to shut down automatically to permit the re-loading of labels into the printer.
Of course, for a label to serve its purpose, such a label must eventually be applied to its intended article. Although the application of labels to articles may be done manually, it has become increasingly more common for such applications to be done with automated equipment. Examples of various types of label applicators are disclosed in the following patents, all of which are incorporated herein by reference: U.S. Pat. No. 6,575,216, inventor Yang, issued Jun. 10, 2003; U.S. Pat. No. 6,550,512, inventor Yang, issued Apr. 22, 2003; U.S. Pat. No. 6,471,802, inventor Williamson, issued Oct. 29, 2002; U.S. Pat. No. 5,785,798, inventor Horsman et al., issued Jul. 28, 1998; and U.S. Pat. No. 4,585,506, inventor Matsuguchi, issued Apr. 29, 1986.
Typically, a label applicator system comprises means for conveying the articles being labeled, means for conveying the label assembly and an applicator plate for use in transferring the labels from the common web of the label assembly to the articles to be labeled. As can readily be appreciated, a label applicator also typically includes registration means for use in synchronizing label transfer from the common web to the articles being labeled and for use in determining when the applicator should automatically shut down once the supply of labels has been exhausted. In most cases, such registration means takes the form of an appropriately positioned optical transmission sensor of the type described above; less often, such registration means takes the form of an appropriately positioned optical reflection sensor of the type described above. As can be appreciated, if the sensor is an optical reflection sensor, the label assembly used therewith must include eye marks.
It should be noted that, although label printing and label dispensing have been described above as being performed by two different types of devices, there do exist combination printer/applicators that sequentially perform the label printing and label dispensing functions.
One type of label that has grown in popularity over the last several years is an RFID (radio frequency identification) label. Referring now to FIGS. 8(a) and 8(b), there are shown fragmentary section and fragmentary, partially exploded views, respectively, of a conventional label assembly of the type comprising a plurality of RFID labels, said label assembly being represented generally by reference number 71. Assembly 71 is similar in most respects to assembly 11, the principal difference between assembly 71 and assembly 11 being that, in assembly 71, in addition to conventional label materials, the label 76 incorporates an RFID inlay 75. As seen in FIG. 8(b), inlay 75, which is sandwiched between face sheet 21 and adhesive layer 19, comprises a carrier sheet 77, the top surface of which is positioned against the bottom surface of face sheet 21, an antenna 79 adhered to the bottom surface of carrier sheet 77, and an IC chip 81 bonded to the bottom surface of antenna 79.
RFID label assemblies of the type described above may be used in printing and/or dispensing devices of the type described above. Typically, such printing and/or dispensing devices are additionally equipped with an RFID tester/programmer that may be used to determine whether the inlay is defective. If the inlay is not found to be defective, the RFID tester/programmer may also be used to program the inlay with information. In the case of a printer, if a label is tested and found to have a defective inlay, the printer head will typically print a marking on the face sheet 21 to indicate to an operator that the label is unusable and should not be dispensed from an applicator. In the case of an applicator, if a label is tested and found to have a defective inlay, the applicator will typically transfer the unusable label onto a dummy article or will keep the unusable label on the web and advance the label assembly to test the next label.
If the percentage of labels having defective inlays were minuscule, the above-described procedure for dealing with defective labels would be adequate. Unfortunately, however, the percentage of labels having defective inlays is currently about 1-20%. Consequently, much time is presently spent by printing and/or dispensing devices in testing labels for defective inlays (some devices testing each label a number of times before concluding that the label has a defective inlay). In addition, because some applicators are designed not to dispense defective labels onto a dummy article, but rather, to keep the defective labels on the web, the presence of a large number of non-dispensed, defective labels on a web may make difficult the re-winding of the web. Furthermore, from the perspective of a label manufacturer, it would be desirable to provide the industrial user of the label with as few defective labels as possible.
Independent of the problems noted above with RFID label assemblies, another common problem involving RFID label assemblies concerns the testing of the inlays of such labels for the purpose of identifying defective inlays. As can readily be appreciated, in order to properly identify defective inlays, one must be able to test one inlay at a time. Unfortunately, however, RFID labels are frequently spaced so closely to one another on a common web (typically about ⅛ to ¼ inch apart) that a reader antenna will elicit readings from not only the inlay of interest but also one or more of its neighboring inlays (such an undesired simultaneous reading of two or more inlays called “a collision”). One approach to this problem would be to space the RFID labels sufficiently apart on the web so that only the inlay of interest will produce a signal. However, as can be seen from the discussion above, if the RFID labels are spaced apart by a significant distance, many printing and/or dispensing devices will mistakenly determine that they are out of labels and will automatically shut down.